[TowerTalk] Grading a ground radial system field strength

[Dinsterdog@aol.com]

Jim,
 
Thank you for your suggestions.  Others have sent me emails agreeing  with 
you.
 
Within what distance would you suggest to measure field strength?   What 
protocol? I would think cranking down the rig to minimal power and taking a  
reading at relative distance of a few hundred feet.  Is there a field meter  out 
their that will accurately read field strength.  I remember Radio Shack  had one 
in the 70's and 80's during the CB craze.  It had a dopey 4 inch  antenna on 
top of it but operated as good as a cereal box decoder ring-  

I've learned several things from experimenting and this question/answer  
round regarding impedance, radials, and SWR on the Cushcraft 4080V multiband  
vertical.
 
First, my radial system added to the Cushcraft  4080V significantly lowers 
the resonant frequency anywhere from +-85KHz on  80M and +-314Khz on 40M.  So it 
doing something considering it is not much  with again, 20 buried radials. 
 
The impedance almost doubles to a higher value on both bands with the  
radials detached. 
But again, the SWR readings are not that effected at resonance.  

The general conclusion of the antenna masters was not to worry about the  
impedance issues but to concentrate on field strength measurements. Obviously,  
the radial system, if graded, is working.  But how well?
 
To know, I'll start my field testing by disconnecting the radials,  measuring 
the signal, the connecting the radials and taking another measurement  to see 
just what difference is.  Then add 10 or more radials and see  what happens. 
 
Of interest to me, and my backyard turf, I am now going to join a radial  
wire from my west antenna which is now in place, to a radial wire of the new  
antenna on the east side.  This way, I will use the existing radial system  for a 
big part of the planned array.  Of course I will add new radials  to the 
system but with a small backyard, I think sharing is a good idea.
 
And I thought impedance mattered- It sure did on my 160M wire Inv  L with 120 
1/4 radials. Thank God for UNUN's
 
With enough radials, it would on the 4080V too. The manual states  that:
 
More than the prescribed number of radials may be installed on the MA8040V  
at your option in order to optimize radiation efficiency.  However, not  that 
as radials are added, SWR may eventually increase to an unacceptable level  as 
driving resistance drops progressively further below 50 ohms. Use the best  
compromise for your operating system." 
 
I have never seen a manual state this. I wish I had the room for too many  
radials!!!!  Well, this is my last posting on things.  Thanks for the  help.  
Once I get the array up, I'll have my field strength meter and let  you know how 
it is going. I'll be sneaking in various backyards at 3 A.M. to  take test 
with my beacon on-
 
73
 
Paul  N0AH